Apparatus and method for reducing edge flash in pulp molded articles



. LEMIEUX I 2,760,412

-R.P APPARATUS AND METHOD FOR REDUCING EDGE FLASH IN PULP MOLDED ARTICLES Aug. 28, 1956 2 Sheets-Sheet 1 Filed Feb. 23, 1952 INVENTOR.

:91. H/S ATTORN Aug. 28, 1956 r R. P. LEMIEUX 2,760,412

APPARATUS AND METHOD FOR REDUCING EDGE FLASH IN PULP MOLDED ARTICLES Filed Feb. 23, 1952 2 Sheets-SheetZ R. LEM/EUX INVENTOR,

H/S ATTOR/VE Y United States Patent APPARATUS AND METHOD FOR REDUCING EDGE FLASH l'N FULP MOLDED ARTICLES Raoul P. Lemieux, Fairfield, Maine, assignor to Keyes Fibre Company, Portland, Maine, a corporation of Maine Application February 23, 1952, Serial No. 273,118

8 Claims. (Cl. 92-57) This invention relates to molding, more particularly to apparatus and methods for molding articles from fibrous pulp.

Edge flashing, or a very thin flange of surplus material, generally forms at the marginal edges on pulp articles molded from dies that have been inuse for some time. This flashing is particularly annoying. The normal resiliency of the pulp makes it impossible to remove fibrous flashing by mere flexure, the simple and usual technique for removing flashing from cured resin articles. Any attempt to positively remove flashing generally leaves the edge of the molded article fuzzy and produces loose fibrous particles which annoy any nearby personnel and also constitute an explosion hazard.

Among the objects of the present invention is the provision of novel molding apparatus and methods which avoid this and related difficulties.

The above as well as additional objects of the present invention will be more readily understood from the following description of several of its exemplifications, considered in conjunction with the acompanying drawings wherein:

Fig. 1 is an elevational view showing a pulp molding apparatus of the invention;

Fig. 2 is a detail view with parts in section of a portion of the apparatus of Fig. 1; and

Fig. 3 is a view similar to Fig. 1 of a modified form of molding apparatus exemplifying the invention.

According to the present invention, it is possible to substantially reduce or entirely prevent the formation of edge flashing on articles made from molded pulp by redistributing the marginal portions of the mass of pulp fibers that is initially loosely formed on the usual suction die. By this redistribution these marginal portions are at least partially commingled with the adjacent portions of the fibrous mass so that there is little if any flash formed at the margins.

For the above purposes redistribution is readily effected by impelling a stream of liquid against the marginal portions of the loosely formed pulp from which the article is made, while suction is applied. The liquid stream renders the fibrous portions against which it is impelled more fluid, while the suction carries these fluid portions onto the adjacent portions of the pulp mass.

Referring more specifically to the drawings, Fig. 1 shows a pulp molding apparatus of the general type described in Chaplin Patent No. 2,163,585, granted June 27, 1939, or in Randall et al. Patent No. 2,234,979, granted March 18, 1941. A forming turret 252 is here shown as carrying a plurality of perforated forming dies 212 through a pulp slurry tank 250 While suction is applied through the die perforations to form a layer of pulp on the successive dies. This layer is then subjected to additional suction after it is withdrawn from the slurry to remove free draining liquid, and is then compacted and dried so that it is ready for use.

In the illustrated apparatus the forming turret 252 I0- Patented Aug. 28, 1956 tates around shaft 254 in the direction indicated by the arrow 256 and carries the formed pulp layers from tank 250 to transfer turret 260 which holds a multiplicity of pressing dies 266 shaped to mate with the forming dies. By proper control of the suction in dies 212 and the application of suction to dies 266 along with compressed air to dies 212 if desired, the formed pulp layers are transferred to the transfer dies and at the same time compacted between dies 212 and dies 266.

The transferred layers can now be subjected to additional compacting and/ or suction, and can also be heated if desired, as by supplying heat to the dies 266 or by additional dies which coact with the transfer turret 260. Pressing turret 274 can also be aranged to remove the pressed pulp layer from the transfer turret and drop them on a conveyor belt 280 which carries them through a tunnel drier for example if they are not already sufliciently dry. The various turrets and other components can be driven in suitable synchronism as by gears such as those indicated at 262, 264.

The perforated forming dies can be of the types shown in the above Chaplin or Randall et a1. patents, or those of Manson Patent No. 2,273,055, granted February 17, 1942, Sheflield Patent No. 1,984,384, granted December 18, 1934, or Louisot Patent No. 2,129,697, granted September 13, 1938. An internal passageway or manifold communicates with perforations shown at 220 in Fig. 2 to suck in liquid from the slurry and trap the fibers of the slurry on a forming surface such as the wire screen 213. A marginal ring 222 is conveniently used to provide a pulp retaining wall or walls 224 for guiding the engagement of the cooperating pressing dies 266 and confining the formed layer of pulp 214 to the desired poritions of the die.

Cooperating dies 266 are provided with pressing surfaces 267 corresponding to the mating surface of die 212, so as to accurately compress the loosely formed layer 214 into the desired shape, and at the same time express some of the liquid present in this layer when first formed. In addition, marginal walls 268 on the pressing dies are shaped to coact with the pulp supporting wall 224 of die 212. For commercial operations some small amount of clearance, usually not more than about 2 to 4 mils (thousandths of an inch), is provided between walls 224 and 268 to limit the escape of pulp during compacting. In normal molding the suction die provides a slight excess of pulp at the periphery, as indicated at 226. Although this helps to assure that the edges of the finished article art not deficient in thickness and thereby unduly weakened, some of the excess pulp will be forced up along the guide walls 224 during the pressing step, particularly if these walls or their cooperating guide walls on dies 266 are worn, nicked or scratched.

According to the present invention however, a spraying structure 240 is arranged to impel an encircling hollow stream of liquid 242 against the marginal edges 226 of loosely formed mass of pulp fibers 214 on suction-forming mold 212 (see Fig. 2). While the liquid stream is so impelled it is advisable to keep suction applied to the forming die 212. The impact of the stream on marginal fibers redistributes these fibers and causes them to readily fiow by reason of the excessive liquid that is present. Under the influence of the suction these readily fiowable fibrous particles are sucked over to the adjacent portions of the interior of the fibrous mass 214. As a result, when the impelled stream is stopped the margins of the formed mass are of greatly reduced thickness, and when compacted show very little or no flashing, even with die clearances of as much as 15 to 20 thousandths of an inch.

The redistributing stream'of liquid is preferably kept as much as possible fromheingimpelled directly'at the central portions of the loosely formed pulp mass 214.

If this is not done, the points at which the stream contacts this intermediate portion will tend to show a displaced fiber structure that gives. rise to-uneven thicknesses and-undue loss of strength. This does notoccurat the periphery apparentlyby reasonofthe'fact'that thereis initially atleast a slight localized 6XCSSj-0f pulp fibers. The liquid stream does have a tendency to apply-sulficient liquid to the pulp mass to cause it to run slightly,.par ticularly where-the formed mass is held in an inclined or vertical; position as: shown in-Fig. 2. :Howevensuch running actually assists in the redistribution of'the marginalfibers, and-the suctionprevents the running from causing any sizeable. shift or flow ofthe fibers'in the:

fiowable pulp "mass.

, Practical: embodiments of the invention can. have'the formingdies stationary or'moving while bei'ng sprayed. Theconstruction of Fig. l is of the first mentioned variety. The turret rotations are arranged to take-place in: discrete steps which carry each die through anarcuate move equal to the distance between theseiindividual'dies.v

Between the steps the turret assembly '2521'is held stationary. Suction, which is appliedat leastwhile the immersed die-2l2 is held stationary in the-slurry to cause formation of the desired fibrous mass, can be maintained through several succeeding steps so that it is still maintainedwhen the die carrying the formed mass reaches the spray position shown in Fig. 1. In the pauseafter this step, the spray structure 240 is actuated for a short period of time. About 1 to 4 seconds is all that is needed where the spraying liquid is water and the spray discharge-passageways are circular with a diameter of about 10 mils and the spray pressure is aboutSO to 60 pounds per square inch. Variations in spray pressure and discharge openings appear to be of substantially no effect so long as the'sprayis vigorous enough to be'directive.

After the spray step is completed the turret assembly 252 advances to the next step where the tormed'fibrous mass onthe nextdie 212- is sprayed, etc. It is not necessary to'rnaintain the forming suction throughout the entire interval between forming and spraying. The suction-canibe interrupted for as long as desired.

The position of-the formed fibrous mass 214 when it is sprayed'is not critical, and can-vary from the horizontal 'to the vertical or can be at any inclination between these two extremes.

The compacting operation by itself may be of long duration toefiect a substantially'coniplete drying of the fibrous article. On the other hand, compacting can very advantageously be limited to a period of one or two seconds,'or the length of-time requiredfor the suction forming of layer 2114. Such short compacting treatments provide all the necessary compactness of the fibrous layer which can then be permitted to complete its drying either in other'dies or without the application of any pressure, as for example on a conveyor belt or one ofthe forming dies. Some-warpage may be experienced with this type of'free' drying, but it is not severe and'may be compensated'for by a final pressing in accurately dimensioned dies.

The technique of the present invention can be used to reduce edge'fiashing' in articles molded from fibrous or non fibrousmasses that include water or other moistening liquid. ln'all of these cases theredistributing action is quitesimilar ineifect. The spraying liquid can be any convenient one including water, with or without additions such as sizing or coloring material.

Fi 'f shows a'variant of the above pulp molding apparatusin which the flash-red-ucing spraying is effected while theformingdiesare in motion. Here the spraying uniPI-tlihas a plurality of nozzles 141 mounted on conduit 139held as'by gears 16-3 to rotate with a forming turret 152. Instead of having this'turret move. in steps,

The spray drive is timed so that the successive nozzles move across the adjacent portion of the forming turret in synchronism with the successive forming dies. Suitable valve action is provided for actuating the spray discharge during this synchronized'movement to effect the desired fiber distribution;

In theform shown in Fig; 3, the spray isc'ontrolled by a fixed valve member'143 which cooperates with the internal surface of the conduit 139 in a manner similar to that of a rotatable sleeve valve. Spray liquid is. delivered from a suitable source to the interior of member 143 andone orlmore'ports 145 in this memberpermit discharge of the liquid througha nozzle 141 when the nozzle moves into'alignment with the ports.

The resulting stream of liquid 142 efiects the desired fiber redistribution as explained above in connection with Fig. 2. It-is notnecessary-tozhave this stream directed extremely accurately at the thickened marginal portions of the formed fibrous mass. The redistribution appears to extendoveran appreciable band of the margin at least about a half: inch or more-inwidth. The small amount tion of this stream impingement pattern in some 'of the positions.

I'nstead of: having 'asingle spray-stream, a plurality o spray steps can advantageously be used for each redistributionoperation. A single spray step usually does not completely level the thick pulp edge'shown in Fig. 2, but by usingifurthersteps, any excess pulp left by the prece'dingstep 'canzbe' further redistributed. to further reduce the excess. Best results appear tobe obtained where the sequence of steps includes a first step more than one second-Tonga last-step less than /2'second long, and intermediatcitst'eps of? intermediate duration, with sufiicientinte'rruption to permit eifective fiber. redistribution between steps. I

'Oneihighly-"efiective example of such a sequence is a combination of four steps theifirst of which takes 1% seconds, thenext two /2 second each, and the fourth /5 second. This sequence produces commercially acceptablelmarginsxin the fi'nishe'd article even though the die guides are'badly marred and scored with clearance gaps in excess of 25 mils.

As'showninFig. -lithe ports 145 can be provided in thedes ire'd numbcr and varied in size to efiiect the desiredi'spray st'eps. The number of nozzles 1 41 canbe equal to, more'than or less than the number of forming dies. Provision should-be made in the constructionof the. apparatus of. Fig. 3 to-assure that the projected stream ofispray liquid'142 reaches the proper potions of the forming dies. Inasmuch as these dies in'their rotation moveitowardiand away from the-plane of closestproximity to the. spray structure, it is advisable to have'the nozzles rotate with a'nangular velocity somewhat lower thanthatindicated by. the relation'of its rotation radius to=that of. the forming turret 152. This permits the projected nozzle stream as it undergoes changes in length" by reason of the varying distance to a moving die, to trace: a pathgenerally conforming to that of the'die. Where theinumber of dies or nozzles are varied, suitable adjustment 'of'the nozzle rotation should be-made.

If. desired, therotating. molding turret can be connected with one oru more nozzles connected to oscillate movesalongwith and is properly directed onto the form.-

ing dies as theyacontinually move past the spray zonei If therequired oscillation frequency is unduly-high, itcan be lowered by oscillating a larger number of nozzles simultaneously, on a single. holder forexample, with each nozzle directed at a diflerent die. In this way a single oscillation cycle can be arranged to simultaneously redistribute the pulp on several diflerent dies.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof it is to be understood that the invention is not limited to the specific embodiments hereof except as defined in the appended claims. Thus for example, the encircling streams of the present invention can be square, rectangular or of any other shape corresponding to the outlines of the articles being molded.

What is claimed is:

1. In a pulp molding apparatus, a tank for holding a pulp fiber slurry, a forming die mounted for movement through said pulp fiber slurry, said forming die having means thereon for depositing a loosely formed, wet mass of fibers on the die face thereof, and a flash reducing mechanism spaced from said tank and in opposed relation to said die face when said forming die is in a predetermined position outside said slurry, said mechanism comprising a projecting device constructed and arranged to project a continuously extending, hollow, fluid spray against the peripheral portion only of said wet mass while said wet mass is on said forming die.

2. The apparatus of claim 1 wherein said forming die is mounted for intermittent movement during which it is held stationary for a predetermined period when it reaches a predetermined position, said flash reducing mechanism being arranged, in timed relationship with said forming die, to project a spray against said die while it is held stationary at said position during said predetermined period and to halt the projection of said spray after the termination of said predetermined period.

3. The apparatus of claim 1 wherein said forming die is mounted for continuous movement into, through and out of the slurry, and wherein said mechanism is interconnected with said forming die to move said spray in conjunction with said die during at least a portion of the path of movement of said die outside said slurry.

4. The apparatus of Claim 1 wherein means are provided to apply a suction behind the die face of said forming die while it is being subjected to the action of said spray.

5. A method for reducing the formation of edge flashing on molded pulp articles which includes the steps of forming a mass of Wet pulp into a desired shape on an open mold face, and then projecting a hollow, continuously extending fluid spray from a spaced, opposed position relative to said open mold face against the peripheral area of the face of the shaped mass While said mass is held on said open mold face.

6. The method of claim 5 wherein a suction is applied behind the face of the shaped mass while it is being subjected to the action of the spray.

7. The apparatus as defined by claim 1 in which the spray mechanism includes automatic control elements connected to operate the spray in groups of spray steps the first step of which is more than a second long, the last of which is less than /2 second long, and intermediate steps are of intermediate duration.

8. A method as defined by claim 5 in which the fluid is impelled in a group of steps the first of which is at least one second long, the last of which is not more than /2 second long, and intermediate steps are of intermediate duration.

References Cited in the file of this patent UNITED STATES PATENTS 432,379 Deering July 15, 1890 1,184,421 Chaplin May 23, 1916 1,707,430 Chaplin Apr. 2, 1929 1,809,852 Jay June 16, 1931 2,163,585 Chaplin June 27, 1939 2,314,203 Fairclough Mar. 16, 1943 2,320,789 Montague et a1. June 1, 1943 2,539,767 Anderson Jan. 30, 1951 2,559,945 Chaplin July 10, 1951 FOREIGN PATENTS 8,685 Great Britain July 18, 1885 6,402 Great Britain 1913 41,964 Denmark Mar. 22, 1930 

1. IN A PULP MOLDING APPARATUS, A TANK FOR HOLDING A PULP FIBER SLURRY, A FORMING DIE MOUNTED FOR MOVEMENT THROUGH SAID PULP FIBER SLURRY, SAID FORMING DIE HAVING MEANS THEREON FOR DEPOSITING A LOOSELY FORMED, WET MASS OF FIBERS ON THE DIE FACE THEREOF, AND A FLASH REDUCING MECHANISM SPACED FROM SAID TANK AND IN OPPOSED RELATION TO SAID DIE FACE WHEN SAID FORMING DIE IS IN A PREDETERMINED POSITION OUTSIDE SAID SLURRY, SAID 